Modulation



Feb. 1s, 1941.-

N'. E LINDEN'BLAD Re. 21717 MOQULATION Original Filed April 5, 19,32 5 Sheets-Sheet 1 Feb. 18, 1941. N. E LINDEN'BLAD l Re- 21,717

' uoDULA'rioN 1 originl Filed April 5, 1932 3 suena-sheet 2 JIM/f /37/ "".flolwi v NILS E.LINDENLAD A SYM/@M ATTORNEY INVENTOR NILS E. LINDENBLAD l ATTORNEY MODULTION D A L a original Filed April 5, 1932 s sheets-sheet 5 nai Ss.

Feb. 18, 1941.

Cil

Reiued Feb. 1s, 1941 Nm E. unanimi, merecer-mn, N; y., mr

to ldlc Corporation of America, a corporation of Delaware Original No. Serial N0.

2,081,947, dated November 24, 1936, 698,496, November 17, 1933, which is a division of Serial No. 603,310, April 5, 1932. Application for reissue February 25, 1938, Se-

rial No. 192.584 y 30 Claims.

This invention, which is ardivision of my copending application Serial Number 603,310, died in4 the United States Patent Office, April 5, 1932, relates to the short wave signaling art and appertains especially to the modulation and electromagnetic propagation of ultra short waves, particularly in the range of wave lengths below two meters and of the order of frequencies above one hundred fifty million (150,000,000) cycles per second.

One object of my present invention is to provide a modulation system for extremely short wave length oscillations of electrical energy.

My present invention will be described more fully hereinafter from which many other objects, features and advantages of my present invention will become self apparent.

In the accompanying drawings,

'Figure l shows a preferred embodiment of my ultra short wavelength modulator:

Figure 2 illustrates a modification of the modulation of Figure l;

'Figure 3 illustrates an alternative antenna arrangement which may be used with either of the systems shown in Figure 1 or 2;

:Figure 4 illustrates still another modified modulating arrangement; and, l

Figures 5, 6, and 'I illustrate still other forms of my present invention.

Turning to Figure 1, energy of fundamental frequency from any suitable source (not shown) is fed through a variable transmission line formed of conductors |32, III of variable length tothe anode circuit or input circultvof the magnetic frequency multiplier' lidFM,which anode circuit is composedI of" conductors |30, |30 directly connected to the anodes |40, |42 of my magnetic frequency multiplier MFM. Within the electron discharge devices or vacuum tubes. i, M0 of my frequency multiplier there are also the control grids or electrodes ill, |00 adjacent the cathodes or filaments |52, |54 respectively. Condensers |53, |55 are in shunt with the diaments |02 and |54 respectively of the magnetic frequency multiplier.

To prevent the'harmonics generated by the frequency multiplier from reacting (or losing energy) backwards upon the source connected to line |32, IM, the conductors |02, Ill are tied on to voltage nodal points or current maximum points or low impedance points for harmonic waves on the tuned anode circuit, of the frequency multiplier formed by conductors |30, |38., With respect tol fundamental waves, the anode ends of the anode circuit are high voltage or high impedance points. These conductors are short cimuited by strap |58 which in turn is grounded through conductor |58. A source of potential, may, if desired, *if

be placed in the conductor |58 to maintain 'the anodes at a suitable Dl C. operating potential. However, I have found in many cases,- for frequency multiplication at these extremely high frequencies, namely, for example, of the order of magnitude of million cycles per second, o r generally, over 100,000 kc. per second; supplied from the master oscillator or other source, that the anodesyl, |42 -can be grounded as illustrated.

The output circuit of the frequency is formed of conductors |00, |62 adjustable in llength and 'tuned toa harmonic, for example, the third harmonic, or in other words, tuned for frequencies of 450,000 kilocycles per second.. as-

suming of course thart the master oscillator 'or other source, connected to lin |52, |54 is adjusted to operate at 150,000 kilocycles per second.

mmupuer The Cathode energizing circuitr for cathodes |52, |54 of electron discharge devices |44, l, consists in general of internal conductors |64, |06 insulated from and supported within the corrcentric external tubular conductors |60, |10. Filament heating current may be traced from con'- ductor 58 through voltage regulating resistance |11 through tuning conductor or strap |14 through the filaments |52, |54 and back through the internal conductors |64, |50 conducting strap or short `circuiting element |18 through con'- ductor |18 to the other side or conductor 42 of the filament heating circuit bus suppliedwith energy from source Il.

By acustment of straps |14 the cathode circuit is tuned for best matching with the rest of the circuits. This means it has a compromise optimum for both fundamental and harmonic fre'- quency. The grid circuit being set for optimum impedance toharmonic energy, this energy read#A ily feeds 'into and flows through the same and mi;

builds up to a large value.

Now,the frequency multiplier as so far de' scribed, namely, without the magnetic apparatus illustrated, will not deliver an appreciable output.

within the. tubes |43, |50, in a direction perpen dlcular to their normal paths 'of travel from nlament to anode. The magnetic apparatus l Toincrease the output, I apply a unidirectional magnetic field to the electron stream consists of a pair of solenoids |80, y|02 through 5;? which runs a yoke |84, preferably of iron of high permeability which may or may not be laminated.` The solenoids Ill, |82 are serially connected as shown. and supplied through -oonf vductors |84, |86 with energizing currents from a line l2 by way oi' an adjustableresistor ill.' 5 It is to be noted that the grids or electrode |48, |50 adjacent the cathodes |52, III are connected to the output circuit formed of conductors |60, |62, within which looped conductorvr iilli is slldably and conductlvely arranged for ilo tuning purposes as well as to allow the direct current voltage, generated by grid rectification. across grounding resistor or biasing resistor |02 to manifest itself upon the control grids or elecatrodes.

jllii y 'I'he resistor |92 is preferably so chosen that the positive peaks of input potential applied to the anodes MII, |42 cause spurts of electrons to impinge upon the control grids or grids adiacent the cathodes. Under such circumstances.

i120 `without the application of the magnetic field.

Athe harmonic output, if any, will be very feeble.l

However, by the application of the longitudinalzly or axially applied unidirectional magnetic `field, the output, at harmonic frequencies in the g5 ftuned output circuit IBI, |62, i is materially I :augmented nd vcfa substantial value.

4A qualitative explanation, as well as a pracyiticalexplanation of this phenomenon is that the electrons emanating from the filaments are au Lcurved in `their paths and retained by the magnctic field in large quantities in suspension in ethe space about the cathodes and closely adjacent the control grids. Hence, when lthe intensity of a positive peak of applied input* po- :35 '.tentialhas grown to suillcientstrength -to bring :the electrons to the grids in spite of the curvl ilng. the number of electrons which splash :against the control grids is considerably larger :than that number without the suspension eil'ect. E In addition, it is to be `pointed out that this iml.proved action may also be due to the factthat Y due to the suspending ofthe electrons within the space `closely-adjacent the control grids.

there is less time difference between the elec- ,a .itrons which travel from the space Suspension to the control grids when arrayed on curves almost 'tangential with the grid relative to the time difference between radially arrayed electrons.

r"I'hese arrays are considered in the sense of the so vmotion of the electronsand not inthe sense of :their actual location. At the high frequencies finvolved, this time lag eifect is, as will be eviident, very important, for, unless the electrons ifimpinge upon the output electrodes in unison.

5&6 `the abruptness of variation requiredto produce Va. harmonic will never be obtained. This is Der- Srhaps better understood if it is pointed out that. :the higher the frequency, the more sodo the telectrons which at a certain moment are con-` @9 pflned in the space. represent the total number y: of electrons taking Dart in an oscillatory cycle. fIn otherwords, due to-theextremely short time duration of a cycle relative to the electron-velocrity it is very important to have the ni'otiovns of the electrons well disciplined so that their action 5in unison will overcome the handicap due to `the absence of mass action which is readily obtained at lower frequencies.

zo "Inns, the application oi Ithe unidirectional :magnetic nel'd cause acharner impingement of relectrons'as well'as cut off of electron i'iowto fthe output electrodes upon the start and cessa'- ition of the positive peaks of input controlling n potentials and it is this sharp vstirtiinriual stoplpresent invention .ing waves'are set up thereon.V and preferablyV maximum potential. IDI, 204. in 00 ping of electron iiow which is responsible to a large degree for harmonic wav C v In general also, improvement in output as well as in many cases, change from non-operation to operation, or, in other words, increased 5 emciency is obtained by the tuning of such circuits as theiilament heating circuits. l

In actual construction. I have used with good success electron discharge devices with reshaped glass envelopes. the longitudinal axes of the ani0 odes of which are substantially parallel to the longitudinal axes of the solenoids illl, ill. Portions oi the tube also have been made to extend 'through openings or orinces drilled' into or tiunugh the magnetic yokes. so that the neldvl intensity applied is increased; and so that leakage iiux is materially reduced. n

It is also to be pointed out in connection withl my improved frequency multiplier that the grids or electrodes adjacent the cathodes, have lbeen 20 v f input is applied to the grids or the plates.

Odd harmonics arefed intol the absorptionclrcuit or modulation link'circuit AS and eventually transmitted by means of transmitting antenna Flor telegraphic signalling, vat some point intermediate the antenna andthe output circuit ofthe frequency multiplier, sknown forms of keying apparatus may be inserted, or known types of4 chopper wheels for that purpose. 35

Enr complex wave modulation however, such as voice modulation, or multiplex signalling, it will be found that the ordinary or conventional schemesof modulation as already pointed out,

fail because of inordinate frequency variation in 40 the tinai output.

Accordingly, avery important feature of my is my improved modulating` system comprising, as illustrated. the absorption circuit or systems AS and the magnetic modu- 4o lator MM.

V'I'lie harmonic frequency output is taken from points of relatively high impedance in the output circuit comprising loop ill through blocking condensers high impedance in the absorption circuit AS. The absorption circuit AS comprises a conductive loop III slidable within conductorsv Ill, ill. This absorption ycircuit is tunedy by adjustment lof lthe loop III within the conductors, ill. III 55 tothe harmonic frequency. A

- Because of the tuned and clod 'condition of the absorption circuit. it is obvious that stand- 'Io points of high the absorption circuit. I couple through conductors Il.. Ill the tlmable control grid circuit III of electron discharge devices lil, 2|! forming part. of my improved modulation system.

As illustrated. the tuned circuit III 'consists of $5 conductors 2 il. Ill within 'which and conductive yly in contact therewith is slidable loop 22| for tuning purposes. '-Iheconductors 2|., tirare connected respectively 'tothe control grids Il! sns m of electron discharge devices zu. m. Y '10,

Astheillamentenergizingorcathode energiziing circuit 226 of my magnetic modulator is identical with that of the cathode energizing circuits heretofore described in connection with my frequency multiplier. I snail not'iiescxibe the'same 7l Y I, I and fed t0 points of a similar 50- as regards desired audio voltages which it is dein detail again. Similarly. the magnetic apparatus for applyinga unidirectional magnetic field to the modulator tubes 212, 214, is identical with that utilized with the frequency multiplier, and the magnetic apparatus 22|, for the magnetic modulator, need not be again described.

It'is to be noted in connection with the m88- netic modulator, that the anodes 22|, 222 are floating, that is, left disconnected. However, ii' desired, a tuned circuit similar to any of the anode circuits described hereinabove, may b e connected thereto. Now, it will be found that if it is attempted to modulate. with conventional schemes,

the energy in the absorption circuit, for example, by by-passing that circuit to ground through a variable impedance in the form of electron discharge devices, variations in the direct current through the impedance device in accordance with modulating potentials will produce only infinitesimal eil'ects upon the energy in the absorption circuit. This is due to the fact that the capacitance of the device prevents any appreciable electron moving voltage to build upat these very high frequencies.' Only by careful lining up of the electrons will it be possible to make them respond to these small voltage variations. Moreover, the low electron velocitywithin the ordinary tubes also mitigates against their use as modulators.

However, with my improved tube absorbing circuit comprising tubes 212, 2I4, modulation is readily accomplished as the characteristics of the tubes are greatly changed, with the application of the magnetic ileld thereto.

In other words, by causing the electrons to be .suspended in orbits near the grid, due to the eiect of the magnetic ileld, a greater number of electrons are available tobe effected by modulating potentials.

The grids are in this case preferably supplied with a positive bias so that they at allftimes are positive. In this way, electrons of tangential motion versus the grid are at all times available in great numbers in the extreme vicinity of the grid so that even though low, potentials of.high

frequency can spend work on the same with the result that absorption takes place.` To vary the potential level upon the control grids of the magnetic modulator, thereby varying the absorption of energy by making a greater or smaller number of electrons available and thereby accomplishing modulation of the waves in the absorption circuit, incoming modulation from a source (not shown) is applied through a transformer 224 to a plurality of electron discharge device amplifiers 236 connected in parallel. These audio frequency amplifiers may have their filaments energized by a source of alternating currents (not shown) through a transformer 23|. Anode potential is supplied through conductor 24| from a source (not shown) in which there is serially connected a choke coil 242 for audio frequency currents. This choke insures the ilow of the varying amplitied modulating currents through a potentiometer or resistor 244.

The 'xed or normal bias on'the control grids of the modulator tubes is derived from resistor 244 through variable tap 246 and conductor 24|. A'choke 250 is placedin series with a conductor 24B for a purpose which will be explained more fully hereinafter. o

As the tapping point 246 giving a correct D. C. bias level for the lgrid electrodes of the magnetic modulator tubes may be erroneously placed potentials l or potentials from. point 24|.

` However, to apply the high audio frequency v arising at point 2|2 to the moduulator control grids, I connect conductor 24| to that point through an audio frequency by-passing condenser 254. which of course is relatively large as compared to a radio frequency by-pass condenser. Thus, by means of this condenserchoke coil arrangement tapped on to resistor 244, I am enabled to apply at the same time to the control grids of the magnetic modulator, the desired high audio frequency voltage and the relatively-low value unidirectional polarizing potential. A

.As already pointed out, the variations in poltential on the control grids of the magnetic modulator tubes vary the amount of energy absorbed from the absorption circuit, as a result of which through adjustable coupling C-2 and transmission line 28| there is fed to the transmitting antenna TA an amplitude modulated wave of substantially constant frequency. The transmission line construction T1..n follows the construction given in my copending United States patent application Serial Number 463,810, filed June 25, 1930. Briefly, the modulated harmonic frequency carrier energy travels-through transmission line 22| through building wall 2|! over transmission lines 26|. 262 and 2|4 to the feeder wires 214 for radiating or transmitting antenna TA, winch is provided with a smooth plane metallic reector 212.

The transmitting antenna comprises a plurality of linear radiators 21| each substantially one-half wave length long arranged coaxially with each other and parallel to another group of half wave radiators 218. The radiators 21| are also coaxiall with each otherl parallel to the radiators 21|. As indicated, the radiators 21|, 21| are formed by.

' bending single conductors 2|l, 2|2. These conductors are so bent that alternate half wave portions thereof form radiating portions as indicated,

the cross portions at 222, 224 being substantially parallel and close together produce substantially cancelling radiations. Hence, by analysis it will be found that the instantaneous currents in the radiating portions 21|, 21| are in like phase as a result oi' which a bi-directional radiant characteristic is obtained. vThis bi-directional characteristic is reduced to a unidirectional characteristic by placing a metallic reflector-212 behind the plane formed by the radiating conductors 21|, 21|

whichare arranged in the same linear plane. The

spacing-between the antenna .system and the smooth metallic reflecting sheet 212 is preferably made substantially one-quarter wave length although any substantially odd quarter wave length v circuited at their rar ends. the input reed from transmission miem being at appoint o: relatively (involved, propagation follows the optical laws fairly close. Consequently. radiation in general, isin a more or less straight line. The reiiector and antenna may be tilted at any angle so, as t'o project, say, a beam of. waves upon a smooth plane reflector situated. say. n the top of a high tower. The reflector mounted on the Itower will in turn reiiect the waves at an angle of reflection equal to the angle of incidence thereon. Forexampie. a transmitting antenna TA may be pointed to a reflector on top of a tower some 500feet high. The reflector may be so positioned that the beam is propagated horizontally until due to the curvature of the earth, it approaches the surface of the earth'. At this point mother reflector may be provided to say, turn the direction of the beam at right angles to the direction up to thatpoint. to a suitable receiver located at some distant point. Preferably. however. due to unavoidable losses during reflection, I prefer to place the transmitting antenna as high as possible and point it directly at a receiving station which may or may not be located in a similar tower. One may also build up systems of curved reflectors with common foci or wire systems with refractive properties. etc.

For repeating any form of iii-direction antenna may be used. for example, if an antenna has two main characteristic ears" the one can be used: forv the incoming signal and the other to repeat vit-in another direction. Even unidirectional antennae may be used providing the incoming repeated signals are on the sameside of the antenna system.

A modified form of my invention for modulating waves of the order in frequency of 450.000 kilocycles per second. is illustrated in Figure 2.

Filament heating or energizing energy for the Ymagnetic frequency multiplier mi is supplied by way of a circuit from a source l which.

though illustrated as a battery, may obviously be any form of unidirectional current. Unidirectional current. of course, for this purpose is preferred although A. C. types of filaments may be utilized. One endof the filament energizing source is grounded as lshown at III.

Fundamental frequency energy is applied to the anodes of the magnetic frequency multiplier MFM. from a suitable source (not shown) connected to the line or conductors I, VIII. Tuning ofthe anode circuit of the magri c frequency multiplier tubes 0. Q may be accomplished as in Figure l by variation of adjustable slides in Vthe anode circuit not shown. The heating circuitV Il! ofthe magnetic frequency multiplier mi is-tuned for best matching for the rest ofthe cir cuit. This tuning may or may not be either the fundamental or harmonic frequency which .it is desiree toproduce.

.The magnetic field. longitudinally .applied to the tubes SII. l in the 'arrangement shown in Figure 2 is accomplished by the action of solenoids Ill, III which may be wrapped about or simply placed about the tubes I, 84|. 4llorewel'. i! desired. the loienoids may be provided I, Ile are in one plane whereas TA of Figure may.

-nlnvlied modulating potentlnls `energy gets through and becomes amr l,

with magnetic cores or the magnetic arrangement may take the forme-described in connection with Figure 1. The intensity of the magnetic4 i'ielrl` is, of course, controlled by the variation of either or both of source I and resistorl.

'.'lhe coupling from circuit AS to theabsorber or modulator tubes I andv Il is shown in' a eimpliiled way. Through .the `action of resistor l lsuitable grid bias is maintained Vupon the grids of the tubes l, illytheiresistor being connected to a short circuiting :conductor 368 variableraiong the conductorsl Ill, .Ill forming part of thecircuit AS as well as the tuned grid circuit. The grid circuit as in Figure l, forms the output circuit of the magnetic frequency multiplier, the short circuiting strap IBI being connected as indicated across voltage nodal points on the circuit AS whereas the conductors IN. III connected to the circuit AS through bypassing condensers Ill, Ill are connected to this circuit at voltage maximum points Ill, 313 thereon, or in other words, at high impedance points. f i

Modulated harmonic frequency energy is taken -from the circuit AS through transmission line TL inductively coupled thereto which. in turn. is also coupled to transmitting antenna TA formed of conductors I, III. This antenna is described more fully in my copending application Serial No. 328.147,l filed Dec. 24. 1928g`patented September v 19, 1933, No. 1,927,522. i

Briefly. due to the nature1 oi wires which are -long relative to the wavelength and due to the relative location of these wires and their relative phase. it will be found that energy is propagated predominantly along the blsector of the angles formed by the conductors 3, III. The attenuation ln the conductors at the high frequencies involved is so great for wires 100 waves long. that there is substan gno reflection. as a result of which no reflector formed of a similar pair of conductors, is required. i

The antenna line TL may be coupled as illustratedlnligureStopairsofconductorssimilar to I, gli. each pair. of course, in a different plane. In Figure 3. the conductors conductors SII. nl are in another the horizontal or vertical planes or any planes intermediate the two. The transmitting antenna either a horizontal or vertical plane. 8nd lthe antennasystemofl'iguresmayberotatedanyangie aboutV the bisector of the solid angle formed bytheconductors. i

Modulation, as already indicated, is accom- Dlished corresponding to amplitudes offthe modulating potentials. from circuit AS by meanaof modulatoror absorber tubes lll, lll. In particular.

i from,` for example. microphone Ill, are fed to an audio amplifier IIC., which. through the action of transformer SII. impresses those potentials through conductor Ill short circuiting strap l `and conductors 402. lll, to the grid of electron being arranged Y plane. These planes may be of course, be arranged in by absorbing variable amounts of energy discharge devices lll, lll of my magnetic modulator. To make doubly sure no fundamental modulated to giveback reaction. short circuiting conductor I is provided. l

.g'l'omaintainproperbiasuponacontrolgrid upon magnetiemodulator mi, a unidirectional source of potential III is provided. As before.

d may be tuned to the harmonic or. in .other words,

to the same frequency as that to which the absorption circuit AS, MM is tuned.

The solenoids 4I4 are energized by a source 4l0 and produce a unidirectional magnetic field which, of course, is applied to the electron flow withinthe modulator tubes 405, 400.

As I have already pointed out, my improved magnetic modulator is the only arrangement wherein desired variable absorption from the .transfer circuit AS can take place.

Certain circuit re-arrangements of this modulator arrangement may be made as for instance illustrated in Figure 4. Modulating potentials in the arrangement shown in Figure 4 are applied to the grid-cathode circuit connected to the parallel connected modulator tubes 420. Direct current potential for both the modulator tubes 420, the magnetic modulator MM, for which, by the way, the magnetic apparatus has been'omitted for the sake of simplicity, issupplied through conductos 422. The modulator reactor 424 is chosen so as to have practically no D. C. resistance. Consequently, the grids and filaments of the modulator tubes 425, `425 will be at the same D. C. potential except for the drop in D. C. potential across resistor 430. However,

since the current drawn through choke 424 is constant through its inherent action, the voltage across resistor 432 connected between the anodes andv cathodes of the modulator tubes 420, will vary according to the modulating potentials due to the varying current flows therein. Con- 40 sequently, the voltage upon the grids of the modulator tubes 426, 42B will vary as a result of which varying amounts of current will be drawn from the absorption circuit AS.

The arrangement shown in Figure 4 oers the 45 advantage that blocking condensers, such as condenser 254 of Figure 1, in a modulation circuit is unnecessary. Moreover, this arrangement shown in Figure 4 has the added advantage that, because of resistance coupling, the circuit is extremely stable, 1s of fine fidelity, and greatly simplifies operation.

Although I have shown the filament, tuning 4conductors to be the means for conveying heating currents to the filaments of the various tubes, heating currents may be supplied through chokes to the filaments, the tuning conductors in that rase carrying only high frequency currents and if desired blocked off from the heating currents by means of large blocking condensers.

My present invention, however, is not limited to push-pull tube arrangements, but may be applied equally as well to single tube arrangements. Also it is not limited to amplitude modulation. For example in Figure 5 I have illustrated diagrammatically an arrangement wherein single tube stages are utilized and wherein the ensuing output is frequency modulated.

The arrangement shown in Figure 5 utilizes a master oscillatorV MO supplying an improved.

single tube magnetic frequency multiplier MFM whose output is frequency modulated and fed to a suitable transmitting antenna TA.

Cathode heating energy for the cathode of themaster oscillator tube 500 is supplied through concentric4 conductor 502, tubular in form, and

` The potentiometer internal conductor 504 after being impressed thereon through the medium oi.' transformer 500. 5l5 is really not needed if the potentiometer 5H is present in the grid circuit. The filament of tube 500 maybe heated by direct current and the arrangement shown in connection with tube 520 may be used wherein the potentiometer 559 serves the dual purpose of regulating cathode bias and cathode heating current. It is to be clearly understod that either arrangement may be used on either tube.`

The slider 500 contacting with tube 502 andv slidable along grounding strip 5I0 (see Figure 6) in turn fastened to grounding plate 52 insulatingly separated from the shield or container 5I4 by means of the condenser dielectric strip 5I5, is used to tune or adjust the impedanceof the cathode high frequencycircuit formed by the tube 502 and in effect ground 5|4.

A similar sliding arrangement SIB is used to tune the grid circuit comprising linear conductor High frequency oscillations generated by the master oscillator are fed from the anode 522 through the adjustable tuning trombone 524,

D.'C. blocking condenser or radio frequency b`y-` Passing condenser 530 to the input electrode or anode 525 of the magnetic frequency multiplier tube 520. The anode circuits of the master oscillator 500 and the magnetic frequency multiplier are formed similarly to the cathode circuit oi the master oscillator and are similarly tuned by means of adjustable sliders 538.

Ihe magnetic frequency multiplier MFM operates similarly. to the magnetic frequency multipliers hereinabove described and is provided with a solenoid 540 in order to apply longitudinally of the tube 520, a unidirectional magnetic field. The output electrode 542 is the normal grid elec trode or electrode adjacent the cathode of the tube 52B and is .tuned to a harmonic of the input frequency by means of slider 558. The cathode circuit of the magnetic frequency multiplier is adjusted in impedance by means'of a slider 568 so that the potentials arising thereon have the most beneficial phase relation for harmonic pro- 'duction in the output circuit including conductors 558 and capacitively grounded strip 554. The output conductor 510 is tapped to a point 512 in the output circuit for most efiicient energy transfer to the radiating linear antenna 514 as illustrated, the transmission line 510 containing an adjustable trombone slide 515. For more perfect balancing, this coupling may be inductive rather than conductive.

In the arrangement illustrated in Figure 5 (and this is true of any of the arrangements heretofore described) frequency modulatedrenergy may be obtained by simply varying the voltage on any of the cold electrodes of the magnetic frequency multiplier and/or master oscillator. The frequency variation thus obtained is at these very high frequencies very much greater in magnitude than the inherently obtained amplitude modulation. For this purpose, in connection with Figure 5, the voltage on the cold electrode 542 of the magnetic frequency multiplier. is wobbled by means of transformer -510 supplied with alternatingv currents from a suitable source 580 and keyed byv means vof a keyer 582. 'I'his alternating voltage from source 580 is superimposed upon the unidirectional voltage impressed upon cold electrode 542.

Similar results could be obtained by inserting the transformer 51B in the anode lead of tube `ist,

' phone or of the masteroscillator tube "l, or, in connectionwith the pushpull arrangements, any similar leads. It is also to be clearly under stood that and the keyer Il! may be replaced by a microsimilar source of alternating currents. The alternating modulating potentials may also be applied in series with the source of energy energizing the solenoid l for modulating pur- P0868.

In the event that it is desired'to radiate from linear radiator 514 an amplitude modulated wave,

Ill. is connected Il grounded by means antenna l" is coupled `to the loop lll by adjustable loop Il! and adjustable transmission line lll. For amplitude energy may be drawn from line I as illustrated by the tube arrangement heretofore described.

Althoughuvarious modifications of my present invention have been described, `it is not limited thereto since many changes will readily suggest themselvesto those reason and since it would be impractical to illustrate every modification of my present invention. it should be clear that it is not t be restricted by the exact descriptions and illustrations given. but solely by the breadth of the appended claims.

YHaving thus claim is:

i. In a modulating system comprising a circuit having high frequency currents owing therein, and, an electron discharge device having an electrode adjacent its cathode connected by ahigh frequency connection to the flow of currents in said circuit, the method of varying the amplitude of current nowing in said circuit which includes varying the voltage on said electrode adjacent the cathode of said device, in accordance with variations to be imparted -to the frequency currents flowing in said circuit, and, subjecting the electron stream within said device to a unidirectional magnetic field.

2. A system for absorbing high frequency energy from a high frequency circuit comprising an A electron discharge device having an electron emitting cathode, and a control electrode, a circuit connecting said control electrode to said high frequency circuit. and a circuit connected with said control electrode for varying the potential on I said control electrode whereby said control elecquency circuit having voltage maximum points,

trode-cathode circuit absorbs energy from said high frequency circuit in accordance with the varying potential applied to said control electrode. 3.v In combination', a tuned high frequency circuit having a high frequency voltage maximum point. and means for varying the flow of high frequency currents in said circuit at a relatively low frequencyrat'e comprising an absorbing circuit connected to saidhigh frequency circuit at said voltage maximum point, said absorbing circuit comprising the impedance between the cathode and a cold electrode in an electron discharge device, said cathode emitting electrons to said cold electrode and means for subjecting the emit.- ted electrons to a unidirectional magnetic field. .I 4. A modulating system comprising a high frethe source of alternating currents lll' varying the conductivity of said skilled in the art. For this c y an electrode adjacent described my invention, what I` said circuit for varying said circuit flowing therein high frequency currents to be modulated, a pair oi' electron discharge devices each having an electron emitting cathode and a cold electrode, means connecting said cold electrodes to voltage maximum points in said high frequency circuit, means for subjecting the electron streams within said devices to unidirectional magnetic action, and, means for devices thereby varying the amount of energy diverted from said high frequency circuit.

5. Apparatus as claimed in claim 4 wherein the cathodes of said devices are connected together by a circuit tuned to a frequency corresponding to that of said first mentioned high frequency circuit. i

6. Means for modulating high frequency oscillations in a high frequency circuit` comprising a pair of electron discharge devices each having an electron emitting cathode, and, a cold electrode; a tuned circuit connecting said cold electrodes together and to a point on said high frequency circuit, a circuit including a reactance to said high frequency oscillations connecting said cathodes together, circuits connecting a point on said high frequency circuit and a point on said last named circuit to points of similar radio frequency potentials andmeans for applyingva magnetic field to the electron streams within said devices.

7. In a modulating system comprising a tuned circuit having high frequency currents 'flowing therein, and, an electron discharge device having its cathode connected by a high frequency connection to a point on said tuned circuit for varying the flow of currents in said circuit, the method of varying the amplitude of current flowing in said circuit which includes varying the voltage on said electrode adsaid device,. in accordance jacent the cathode of with modulating potentials to be impressed on the high frequency currentsflowing in said circuit, and simultaneously subjecting the electron stream in said device to a unidirectional magnetic field of substantially constant'strength perpen dicular to the path of said electron stream. n

8. Modulating apparatus to be used with a high frequency circuit comprising an electron discharge device including an electron emitting cathode and an auxiliary electrode, a circuit con- Y necting said auxiliary electrode to said high freoscillations comprising an electron discharge device having an electron emitting cathodeand an auxiliary electrode, a'circuit-connecting said auxiliary electrode to a point of substantially fixed radio frequency potential, means for tuning a portion of said last named circuit to resonance at the frequency of said ultra high frequency to be modulated, a tuned circuit connecting said cathode to said point of fixed radio frequency potential whereby relative oscillations at said ultra high frequency between at least one of said electrodes and said point is produced; and means -for applying modulating potentials vto the auxiliary electrode.

said last named circuit to reslill? 10. Moduiating apparatus comprising a pair of electron discharge devices each having an electron emitting cathode and an auxiliary electrode, circuits vconnecting the auxiliary electrodes of said discharge devices together and to a point of substantially fixed radio frequency potential, circuits connecting said cathodes of said devices together and to a point of substantially fixed radio frequency potential, means for tuning each of said last named circuits to resonance at ultra high frequency, whereby said cathodes oscillate relative to said point f substantially fixed radio frequency potential, and a circuit for applying mod-- ulatin'g potentials between said auxiliary electrodes and said cathodes.

i1. Moduiating apparatus as recited in claim l0, in which the circuits connecting said auxiliary electrodes together are each turned to resonance to ultra high frequency.

12. Moduiating apparatus as recited in claim 8, including means for producing a magnetic field of substantially fixed strength in the path along which the electrons emitted by said cathode when energized ow.

13. Moduiating apparatus as recited in claim 8, n which a source of potential is connected to said electron emitting cathode by way of said circuit connecting said cathode to a point of substantially fixed radio frequency potential.

14.- In a modulating system to be used with a high frequency circuit, anelectron discharge device including an electron emitting cathode and an auxiliary electrode, a circuit connecting said auxiliary electrode to said high frequency circuit and to a point of substantially fixed radio fre- `quency. potential, a circuit connecting said electron emitting cathode to a point of substantially fixed radio frequency potential, a reactance in said last named circuit which offers Aa high impedance to the iiow therein of oscillations of a frequency of the order of the frequency to which said ultra high frequency circuit is tuned, and means for applying modulating potentials to said auxiliary electrode.

l5. A modulating system as recited in claim 14 in which a capacity and inductance is included in said last named means.

16. In a modulating system to be used with an `ultra high frequency circuit, an electron discharge device including an electron emitting cathode and an auxiliary electrode, a circuit connecting said auxiliary electrode to said ultrahigh frequency circuit and to a point of substantially fixed radio frequency potential, a circuit connecting said electron emitting cathode to a point o f substantially fixed radio frequency potential, a reactance in said last named circuit of high impedance to oscillations of a frequency of the .order of the frequency of said first nax'ned circuit, means for applying modulating potentials to said auxiliary electrode, and means forV applying a magnetic field 'to the electron stream within said device. I

1'7. A modulating apparatus asl recited in claim 10 including means for applying a magnetic field of substantially xed strength to the electron' streams within said devices.

18. In a signalling system, a first tuned high frequency circuit, an electron discharge device having an electron emitting electrode and a gridlike electrode in the emission pathr ofsaid emitting electrode, a second tuned circuit connecting said grid-like electrode to a point on said tuned high frequency circuit, an impedance connecting a different point on said tuned high frequency circuit to a point of fixed high frequency potential.,va third tuned circuit of high impedance to oscillations of the frequency to which said first named circuit is tuned connected between said electron emitting electrode and said point of fixed high frequency potential, a source of heating current for said emittingl electrode connected to said third named circuit and means for varying.the impedance of said device at signal frequency. y

19. In a signalling system, a tuned high frequency circuit. a pair of electron discharge devices, each havingan electron emitting electrode and a grid-like electrode in the emission path Vof said emitting electrode, a second tuned circuit connecting' said grid-likel electrodes to spaced points on said first named high frequency circuit. an impedance connecting different points on said high frequency circuit to a point of fixed high frequency potential, a third tuned circuit of high impedance to oscillations of the frequency to which said first named tuned circuit is tuned, connected between said electron emitting electrodes and said point of xed high frequency potentlal, a source of heating current for said emitting electrodes connected to said third named circuit and vmeans for varying the impedances of said electron discharge devices at signal frequency.

20. In a. signalling system a tuned high frequency circuit, a pair of electron discharge devices, each having an electron emittingelectrode, a grid-like electrode in the path of emission of said emitting electrode and a plate-like electrode, a secondtuned circuit connecting said grid-like electrodes to spaced points on said first named high frequency circuit, an impedance connecting different points on said first named high frequency circuit to a point of fixed high frequency potential, a third tuned circuit, on high impedance to oscillations of the frequency to which said first named tuned circuit is tuned, connected between said electron emitting electrodes and said point of fixed high frequency potential, a source r wherein the impedances of said devices are varied in phase at signal frequency.

23. Ina' modulation system, frequency oscillations to be modulated, an output circuit, a transmission line comprising two conductors coupling vsaid source to said output circuit to supply wave energy from said source to said output circuit, a pair of electron discharge devices each having an electron emitting cathode and an auxiliary electrode, separate means coupling each of said auxiliary electrodes to a different conductor of said line, a source of a source of highv modulating potentials, and means for varying' the conductivity of said devices in phase in accordance with potentials from said source of modulating potentials. 24. A system as recited in claim 23 wherein the coupling means between said line and auxiliary electrodes are substantially a multiple of a quarter wave length long.

25. Moduiating apparatus comprising a pairy of electron discharge devices each having van electron emitting cathode and an auxiliary elec-V z said cathodes.

26. In a` system for absorbing from a high frequency line, an amount of highfrequencywave energy controllable at signal frequency to thereby produce amplitude modulated high frequency wave energy, a line comprising two conductors, a source of high frequency wave energy, means coupling a terminal of each rofqsaid conductors to said source, said source impressing high frequency exciting energy on said conductors to produce in said line, high frequency oscillating voltages of the frequency of said high frequency wave energy, a load impedance coupled to the free a pair of electron v terminals of said conductors. discharge devices each having an electron emission element and an additional element, -a high frequencyconnection between the'additional element of. one of said devices and a point on one of said rst conductors, a high frequency connection between the additional electrode of the other plitude modulated of said devices and a'point; on conductors, means connecting ments of said devices together, a source of .modulating potentials, and means connecting said sourceV of modulating potentials to said devices the other of. said the emission eleto vary the 'impedances thereof in phase in accordance with the said modulating potentials tor4 thereby vary the amount of high frequency 4wave energy absorbed by said devices from said line comprising said two conductors. Y

27. In a system forabsorbing from a line, an amount of high frequency'wave energy controllable at signal frequency to thereby produce amof a length which is a multiple o f a quarter wave length of thehigh .frequency wave energy, a

coupling impedance excited by high frequencywave energy to be modulated connecting a terminal of one of said conductors to a terminal of the `otherof said conductors to produce in said' line, high frequency oscillating voltages of the frequency of said high frequency wave energy to be modulated, a load impedance coupled to the free terminals of said conductors. a pair of electron discharge devices each having an electron emission element and anadditional element, a high frequency connection between the additional element of one of saiddevices and a point on one of said conductors, ahigh frequency connection between theadditional electrode of the other of said devices and a point on the other of said conductors, means connecting the emission elements'of said devices together and to both of said conductors, a source of modulating potentials, and means connecting said source of modulating potentials to said devices to vary the impedances thereof in phase in accordance with the said modulating potentials to thereby vary the amount of high frequency energy absorbed by said devices from said line comprising said two two conductors." l

28. In an amplitude modulation system, a

source of high frequency wave energy of substanapplying modulating line comprising high lfrequency wave energy, a transmission line: comprising ltwo conductorstially constant frequency. aV transmission -line comprising two linear conductors each of a length which is a multiple of a-quarter wave length of the high frequency wave energy of said source, a coupling reactance excited by high frequency wave energy from said source to bemodulated connecting a terminal of one-of said conductors to a terminal'of the other of rsaid conductors to producey in said line, high frequency oscillating voltages of the frequency of said high frequency wave energy to be modulated, a load impedance coupled to the free terminals of said conductors, a pair of electron discharge devices each having an electron emission element and an additional element, a high frequency conductor connecting the ladditional element oi point on one of said rst conductors, a high frequency conductor connecting the additional electrode of the other of said tubes to a point on the other of said first conductors, means connecting the emission elements of said devices together and tov both of said first named conductors, a source of modulating potentials, and means connecting said source of modulating potentials to said tubes to vary the impedances thereof in phase in accordance with the said modulating potentials to thereby vary theamount of high frequency energy absorbed by said tube from said said two conductors.

29. In a short wave length modulation system, a load impedance, a two-wire line having one terminal connected to said load impedance. means for causing high frequency wave energy to flow in said two-wire line to supply energy from said line to said load impedance, and means for modulating theenergy in said line and consequently the energy supplied to said load impedance comprising a pair of electron discharge devices each having an electron emitting cathode and a plurality of f auxiliary electrodes, means coupling one of said auxiliary electrodes in one of said devices to one'of the wires of said line,4 means coupling the corresponding auxiliary electrode in the other' of said devices to the other wire of said line, means connecting the cathodes `of. said devices together; a connection between corresponding auxiliary vices, named connection and the said means connecting the cathodes of said devices together whereby the impedances between said last named corresponding electrodes and the cathodes of said devices are in parallel, and means for impressing modulating potentials on said last named impedance to control the conductivity of said devices in phase at signal frequency to thereby control the amount of high frequency energy absorbed from said two-wire line by said devices.

30. In a short wave length modulation system, a load impedance, a two-wire line having one terminal connected to said load impedance, means for causing high frequency wave energy t0 flow in said two-wire line to supply energy electrodes o f said deone of said tubes to a.

:sav

an impedance connectedv between said last from said line to said load impedance and means 1o the anode of said additional electron discharge device to said impedance, and means for impressing modulating potentials from said source of modulating potentials on-the control grid and cathode of said additional device to thereby modulate'the impedance of said additional device at signal frequency and consequently control the amount of high frequency energy absorbed from said two-wire line by said rst named pair l of devices at signal frequency.

NILS E. HNDENBLAD. 

